In a notebook PC, a first casing provided with a keyboard portion is coupled in general via an opening and closing device to a second casing provided with a display equipment, etc., such that both casings can open and close relative to each other in a terminal device. In the above-mentioned opening and closing device, a lock holding means is provided for maintaining a locked state of the second casing in a closed state relative to the first casing.
The lock holding means of the opening and closing device converts a spring force of a disc spring urged in an axial direction of a second hinge shaft into a rotation torque around an axis of the second hinge shaft and urges the second casing in a closing direction.
Then, a opening torque for rotating the second casing in an opening direction is a sum of a spring torque converted in a cam mechanism and a friction torque of a free stop tilting mechanism. As spring torque converted in the cam mechanism, a large torque is generated, when a cam follower rides over a cam top of a cam portion.
For this reason, when the second casing is opened relative to the first casing in order to use the terminal device put on a desk, it requires a great force on one hand and the first casing is as well raised up on the other, which are problems in terms of use and operation of the terminal device. The known art which describes the above-described opening and closing device includes JP Laid-Open Patent Application No. 2015-180833 (FIG. 7, paragraph [0030]).